It is well-known to provide sockets having electrical contacts in electrical devices such as lighting fixtures having light bulbs. Certain well-known, older styles of light bulb sockets are threaded for receiving threaded bulbs. Certain track lighting sockets, such as those used with "PAR-36" style bulbs, include electrical wires having, at ends thereof, fork terminals that are attached to screws on the back of the bulb. Attachment of the fork terminals to the bulb is time-consuming chore that must often be performed under adverse conditions, such as while standing on a ladder.
More modern sockets, such as those used with track lighting, are of the so-called quick connect type and permit installation and removal of light bulbs, such as PAR-36 bulbs, upon forcing a male terminal member of the bulb between a pair of spring arrangements, or spring terminals, that function both as electrical contacts and as means for holding the bulb in position. The spring terminals are generally mounted inside of a contact cover into which wires are passed and connected to the spring terminals.
The prior art spring terminals typically comprise a first, substantially U-shaped, highly resilient member, usually formed from a single piece of conductive metallic material. The male terminal member of the bulb is forced between the legs of the first member, the legs being connected to each other by a common web and acting as leaf springs. The legs of the first member are typically provided with corrugations extending laterally across the width of the first member to facilitate retaining the male terminal member in the space defined by the legs. A strip-like portion of the male terminal member is received in the corrugations and contacts the legs to form an electrical connection. There is, therefore, little surface area contact between the legs and the male terminal member.
The leaf spring legs of the first member, standing alone, tend to only weakly clamp the male terminal member between them. Further, over time, the leaf spring legs tend to lose tension and function even less well as clamps. The poor clamping of provided by the legs tends to result in poor electrical contact with the male terminal member of the bulb, particularly in view of the limited amount of surface area contact between the legs and the male terminal member, which may result in arcing and solder melt and premature lamp failure.
Spring backers, which are usually in the form of substantially rigid U-shaped members, are generally provided to offer additional strength to the legs of the first member. The first member is disposed between legs of the spring backers, the legs of the spring backers being shorter than the legs of the first member to permit bending of the legs of the first member for installing or removing a bulb. However, while spring backers improve the operation of the first member, the legs of the first member nonetheless tend to lose tension over time, provide poor clamping power, and provide poor electrical contact. Moreover, the spring backers comprise yet another component of a socket assembly and increase assembly difficulty and cost.
Prior art spring terminals are typically connected to wires by means of a tubular prong that extends off of the web connecting the legs of the first member. Stripped ends of the wires are received in the tubular prong and are crimped or soldered therein. The prongs are typically pointed in opposite directions, facing away from each other, to minimize the possibility of shorting. This arrangement tends to require the wires to be bent significantly over relatively short distances, and requires large amounts of wire inside the relatively small contact cover.
It is desirable to provide a socket having quick connect spring terminals that provide good clamping and electrical contact properties. It is further desirable to provide a socket having quick connect spring terminals that require few parts, are simple to assemble, and are low in cost.
In accordance with one aspect of the present invention, a spring terminal formed of electrically conductive material is provided. The spring terminal includes a central web, and a left and a right spring assembly. Each spring assembly is substantially U-shaped and includes first and second legs interconnected by a bight. A first leg of each spring assembly is attached to the central web and extends therefrom toward a respective bight. A second leg of each spring assembly extends toward the central web from a respective bight. Both second legs of the spring assemblies are disposed between the first legs and define a socket together with the central web. The second legs are flexible with respect to the central web in directions toward and away from each other.
In accordance with another aspect of the present invention, a method of making a spring terminal is provided. According to the method, a flat sheet of conductive material is provided. A left and a right end of the conductive material are bent relative to a central region such that the left and right end are substantially perpendicular to the central region. The left and right end are also bent such that edges of the left and right end are disposed proximate the central region and define, with the central region, a socket.
In accordance with yet another aspect of the present invention, a socket assembly is provided. The socket assembly includes a pair of spring terminals formed of an electrically conductive material. Each spring terminal includes a central web, and a left and a right spring assembly. Each spring assembly is substantially U-shaped and includes first and second legs interconnected by a bight. A first leg of each spring assembly is attached to the central web and extends therefrom toward a respective bight. A second leg of each spring assembly extends toward the central web from a respective bight. Both second legs of the spring assemblies are disposed between the first legs and define a socket together with the central web. The second legs are flexible with respect to the central web in directions toward and away from each other. The socket assembly further includes a contact cover. The pair of spring terminals are mounted inside of the contact cover such that the sockets of the pair of spring terminals are aligned with each other.